200 Mr, Bray lei/ on t lie 7iew Varieties of Cafbon, [Sept. 



tion, from the liquid to which the gaseous carbon is reduced; so 

 that the successive depositions, arising from the repeated pro- 

 ductions of carbon, foi*m the stratified mass ? 



I intended to have concluded this paper with a few remarks, 

 suggested by Dr. Colquhoun's details, on some other forms of 

 carbon, existing in nature, as well as resulting from the processes 

 of art ; and on the prevalence of that body throughout nature, 

 and its presence, as well as that of sulphur, in every stage of 

 the fonnation of the crust of the earth, from that in which the 

 primaiy rocks were produced, down to the era of the newest 

 tertiary beds. But I have extended the foregoing observations 

 to so great a length, that I must reserve these for a future 

 opportunity. It would, however, be uncandid, as well asunphi- 

 losophical, were I to conclude, at present, without noticing a fact, 

 that appears to mihtate, in some degree, against the hypothesis 

 I have advanced, that the liquid state is necessarily intermediate 

 between the solid and the aeriform ; and which I must acknow- 

 ledge I do not as yet understand. This is the evaporation of ice 

 and snow, without any previous visible liquefaction, at tempera- 

 tures that would immediately condense aqueous vapour from any 

 other source, into snow itself. The most satisfactory experi- 

 ments on this subject, that I am aware of, are those recorded by 

 Mr. Luke Howard. In one of them, 2600 grains of hard snow 

 lost 27 grains by evaporation in ten hours, the temperature 

 varying only between 12° and 28°.* Perhaps, however, the 

 fact may admit of this explanation. The tendency to assume 

 the vaporous state, which is sufficiently strong to overcome the 

 cohesive attraction of the solid ice, at such low temperatures, 

 may also be sufficient, to cause the instantaneous passage of the 

 water, its first operation on the ice must be supposed to produce, 

 into aqueous vapour. At all events, the existence of the vapour 

 of water at a temperature so far below that required for its soli- 

 dification, with the additional condensing power of radiation 

 from the surface of the snow, is as apparently anomalous, as the 

 instantaneous production and evaporation of water, presumed in 

 my view of the case, can be imagined to be. 



Before 1 terminate this communication, I would also notice 

 the production of a solid ingot of copper from the solution of 

 a salt of that metal, which Dr. Colquhoun alludes to as being so 

 anomalous. It is possible, that, in this case, as well as in that 

 of the formation of the capillary carbon, I may have overlooked 

 the difficulty. But I am unable to perceive any thing in the 

 process, that cannot be readily explained. The oxide in the 

 solution of a cupreous salt is diffused throughout the solution, 

 of which every drop contains a portion. Now when this oxide 

 is reduced, by its oxygen passing to the plate of iron immersed 



* Climate of London, vol. i. notes to Tab. xc. 



